Conventionally, examples of connecting methods for connecting a member-to-be-connected, such as a flange, to a pipe includes the following method.
A pipe is inserted into an insertion hole formed in a member-to-be-connected, and an expanding die is placed in a hollow portion of the pipe. This die has a wedge hole portion and is divided into a plurality of die segments in the circumferential direction thereof centering around the wedge hole portion. Next, an expanding mandrel is inserted into the wedge hole portion of the die to thereby move each die segment of the die in the radially outward direction of the pipe. With this, among the inserted portion of the pipe inserted in the insertion hole and both axially adjacent portions of the inserted portion, at least both the axially adjacent portions are enlarged in diameter (i.e., radially expanded) to thereby connect the member-to-be-connected to the pipe. This connecting method is also called a ridge lock method (see, for example, Patent Documents 1 to 3).
According to this connecting method, both the axially adjacent portions of the inserted portion of the pipe are locally pressed from the inside of the pipe, forming diameter enlarged tubular portions outwardly expanded at both the axially adjacent portions. The member-to-be-connected is connected to the pipe in a state in which the member-to-be-connected is clamped by and between these two diameter enlarged tubular portions. With this, the joint strength of the member-to-be-connected with respect to the pipe axial direction is enhanced.
Each die segment of the die is integrally provided with two pressing protruded portions for forming the two diameter enlarged tubular portions on the outer periphery at a distance in the axial direction of the die (i.e., in the axial direction of the pipe).    Patent Document 1: Japanese Unexamined Laid-opened Patent Application Publication No. H11-36859    Patent Document 2: Japanese Unexamined Laid-opened Patent Application Publication No. H11-47855    Patent Document 3: Japanese Unexamined Laid-opened Patent Application Publication No. H4-8818 (page 2, FIG. 8)